This invention relates to a machine tool and in particular relates to an improved tool holder and/or spindle in a machine tool.
In general, a spindle of a machine tool has a supporting portion for a tool holder. An inserting portion of the tool holder is inserted into the supporting portion so that the tool holder is attached to the spindle. An outer surface of the inserting portion is covered by a layer made of a cemented and hardened steel, hard chromeplating, or other cemented metals.
Many tool holders are often exchanged between the spindle and a tool magazine by means of a tool changer. When the inserting portion of the tool holder engages the supporting portion of the spindle and a supporting portion of the tool magazine, some friction is produced between them so that the inserting portion of the tool holder is apt to be easily worn. For such a reason, it becomes incomplete to attach the tool holder to the spindle and/or the tool magazine. In other words, the life time of the tool holder is short.